Method of forming an engraved plate

ABSTRACT

An engraving blanket which comprises an engraveable layer of live resilient rubber material vulcanized at one face to a face of a base layer of nonhard, nonresilient rubber material. Talcum powder is evenly dispersed between the vulcanized faces of the two layers to control the degree of adhesion between the two. This permits selected portions of the engraveable layer to be cut out and stripped from the base layer to produce a printing design and yet provides sufficient adhesion to keep the layers together during use of the blanket. The disclosure also relates to the method of making the engraving blanket.

United States Patent 1191 8/1926 Stedman 156/248 X 11] 3,818,832 Coaleet al. 14 June 25, 1974 [5 METHOD OF FORMING AN ENGRAVED 1,597,4328/1926 Conant 1. 156/289 x PLATE 3,002,231 10/1961 Walker et al. 156/289X 1 3,180,260 4/1965 Joseph 101/401.1 Inventors: as -v oa Pensacola;Sldney 3,276,947 10/1966 Waterman 101 /415.1 x

W. Gunn, Cantonment; Frank Merrigan; Donald Tompkins, FOREIGN PATENTS ORAPPLICATIONS both of Pensacola, all of Fla. 100,912 5/1937 Australia101/395 [73] Assignee: St. Regis Paper Company, New

York, NY. Primary Examiner-Clyde l. Coughenour Attorne A em, orFirm-Woodlin ,Krost, Gran er [22 Filed; Aug. 2, 1972 & Rusty g g g [21]Appl. No: 277,281

[57] ABSTRACT U-S. An engraving blanket comprises an engraveable 156/289layer of live resilient rubber material vulcanized at one [51] f CL 1/021332b 31/12, B3219 31/18 face to a face of a base layer of nonhard,nonresilient 158] Field of Search 156/248 289; 101/395 rubber material.Talcum powder is evenly dispersed 101/401, 401-] between the vulcanizedfaces of the two layers to control the degree of adhesion between thetwo. This per- [56] References Cited mits selected portions of theengraveable layer to be UNlTED STATES PATENTS cut out and stripped fromthe base layer to produce a 1,093,310 4/1914 Carkhuff 101/368 x Printingdesign and y Provides Sufficient adhesion to 1,195,311 8/1916 White156/239 x keep the layers together during use of the blanket. 1,367,1802/1921 Darrow.... 156/289 X The disclosure also relates to the method ofmaking 1,534,527 4/1925 Joseph |O1/401.1 X the engraving blanket, 11,589,665 6/1926 Schmutz 101/395 1,595,581 3 Claims, 3 Drawing lFiguresPAlENfEnJunzsmm 3818.832 sum; are- I 1 METHOD OF FORMING AN ENGRAVEDPLATE The present invention relatesin general to what are commonlyreferred to as engraving blankets where a printing design is produced atthe printing face of the blanket to perform a printing function.

Many prior art blankets include a cover sheet of a rubber compositionwhich has a base or backing sheet of a canvas or cloth construction. Inthese constructions, problems arise in that the edges of the backingsheet fray and raise, causing problems during the printing operation.Frayed or raised edges cause undesirable lines or smudges in theprinting operation.

Other prior art designs have involved the use of two or more layers ofrubber-like material; however, no provision has been made to provide forthe easy removal or stripping of selected portions of the printing layerfrom the base layer to form a printing design.

In'the design of the engraving blanket of the present invention theproblems involved with the canvas or cloth backing sheet havebeenobviated in that both the top engraveable layer and the base layerare constructed of a rubber composition without the use of cloth orcanvas. In the present design provision is made for the convenientremoval or stripping of selected portions of the engraveable layer toproduce a desired printing design by placing a small but effectiveamount of an extremely fine grit talcum powder between the engraveablelayer and the base layer before vulcanizing the two layers together in apress.

It is, therefore, an object of the present invention to provide anengraving blanket which obviates the abovementioned difficulties of theprior art and which is economical to produce, reliable in operation andhas a substantial longevity.

Other objects and a fuller understanding of this invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is an isometric view of a step in making the engraving blanket ofthe present invention;

FIG. 2 is a fragmentary elevational view showing an other step in makingthe engraving blanket; and

FIG. 3 is an isometric view of the completed engraving blanket.

FIGS. 1 through 3 best illustrate the method of making and the finishedconstruction of the engraving blanket of the present invention and FIG.1 illustrates the placing of an engraving layer 22 of a rubbercomposition into contact with a plate of magnesium engraving metal 24. Aprinting face 26 of the engraving layer 22 is placed in contact withplace 24 and this is to provide a very fine finish for the face 26because of the nature of the magnesium from which the plate is formed.The engraving layer is also provided with what will be described as astripping face 27.

After the engraving layer has been so placed, the

stripping face 27 thereof is provided with a fine grit talcum powder 28evenly dispersed over the surface thereof. The talcum powder isdispersed in an amount on the order of one-fourth gram for each squareyard of stripping face 27 surface area.

A base layer 30 of a rubber composition having a stripping face 31 isnext brought into contact with the engraving layer 22 with the faces 27and 31 together and with the talcum powder 28 sandwiched therebetween.If desired, the talcum powder may be applied to face 31 of layer 30before face 31 is brought into contact with face 27.

The so assembled plate 24, layer 22 and layer 30 are next placed in avulcanizing press (FIG. 2) which includes upper and lower platens 35 and36. The unvulcanized rubber composition layers 22 and 30 are vulcanizedtogether in the press at a temperature of on the order of 130C for about15 minutes.

The assembly is then removed from the vulcanizing press and any flash ofrubber composition is removed from around the edges of plate 24. Thevulcanized layers 22 and 30 are removed from plate 24 and if desired theexposed surface of the base layer 30 may be ground to produce theoverall desired thickness of the engraving blanket 20 which is thenready for engraving. As an example, the total thickness of the engravingblanket 20 may be on the order of 0.1 10 to 0.112 inch.

FIG. 3 illustrates the engraving process and here it will be seen thatthe letters S and R are produced. This is accomplished by utilizingajsharp instrument such as an engraving knife and cutting through theengraving layer 22from the printing face 26 down to the contiguousstripping faces 27 and 31. The cut portions of engraving layer 22 arethen stripped from face 31 of the base layer 30 to define the voidsindicated by reference numeral 34 and the letters S and R are formed ofthe portion of the engraving layer which remains. The engraving blanketis now ready to perform its printing function by the application of aprinting fluid to the printing face and impressing the same onto anobject which is to beprinted.

The rubber composition of the engraveable layer is an engraving gumstock of a live and resilient nature which is capable of a life of up toone million printing impressions. It may be a natural rubber compositionhaving a Shore Durometer (Shore A) Hardness of on the order of 50-55after vulcanization. It may also be a vulcanizable polyblend made bymixing a polyvinyl chloride with a rubbery nitrile copolymer rubber withthe vulcanizate exhibiting a Shore Durometer (Shore A) Hardness of onthe order of 50-55.

The rubber composition of the base layer is best described as beinganonresilient (i.e., dead), nonhard material which is compatible forvulcanization with the material of the engraveable layer. It may be of anatural or synthetic composition but is preferably a vulcanizablenitrile rubber which exhibits a Shore Durometer (Shore A) Hardness of onthe order of 50-55 after vulcanization. The nitrile rubber used is abutadieneacrylonitrile copolymer with the butadiene content being morethan 50 percent of the total weight. The nature of the base layermaterial is such that it is resistant to creeping or stretching as theengraving blanket is used.

The resiliency of. the engraveable layer is relatively high compared tothe resiliency of the base layer. In tests on standard rubber reboundingtest machinery it has been found that the engraveable layer has arebound value of on the order of 177 and the base layer in one instancehad a rebound value of about and in another instance a value of about69. The figures represent comparative values with the higher the numberrepresenting the greatest rebound. It will be seen that the engraveablelayer has at least two times the resiliency as the base layer.

The talcum powder 28 used is for the purpose of controlling the degreeof vulcanization between the en- 3 graving layer 22 and the base layer30. This can be explained in terms other than the amount of talcum usedand the terms are the amount of force necessary to pull the two layersapart. The test to determine the force is made on what is known in theart as a Scott Model X-3 Test Machine. A sample of the engraving blanketof a size 1 inch X 10.25 inches is cut from the roll in the fillingdirection. The two layers'are stripped away from each other a distanceabout 1 inch to 1 /2 inches. The sample is placed in the Scott Model X-3and run at a speed of 2.5 inches/minute. A reading in pounds is recordedand the preferred adhesion between the layers in this invention gives areading between 6 and 8 pounds.

It will thus be seen that the construction of the present inventionprovides for the convenient preparation of the printing face of theengraving layer and does away with the problems of blankets whichutilize a canvas or cloth backing. The blanket of this invention iseconomical to produce and has a long commercial life.

Although this invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

- having a stripping face, uniformly adding a small but effective amountof talcum powder on the order of onefourth gram for each square yard toat least one of said stripping faces, placing the stripping face of saidfirst layer into contiguous contact with the stripping face of saidsecond layer, placing the first and second layers in a vulcanizing pressand vulcanizing the two layers together, cutting through the printingface of said first layer down to said stripping faces in a given patternand stripping the pattern of said first layer from said second layer toleave indicia for printing at said printing face of said first layer.

2. The method as claimed in claim 1, wherein said rubber composition ofsaid engraveable layer is a vulcanizable natural rubber or avulcanizable polyblend of polyvinyl chloride and a nitrile rubber andsaid rubber composition of said base layer is a vulcanizable nitrilerubber.

3. The method as claimed in claim 2, wherein the Shore Durometer (ShoreA) Hardness of the engraveable layer and the base layer are on the orderof 50 55.

1. The method of making an engraving blanket including the steps ofproviding a first layer of relatively live relisient material of arubber composition and having a printing face and a stripping face andproviding a second layer of relatively nonhard, nonresilient materialcompatible for vulcanization with the material of the first layer andbeing of a rubber composition and having a stripping face, uniformlyadding a small but effective amount of talcum powder on the order ofone-fourth gram for each square yard to at least one of said strippingfaces, placing the stripping face of said first layer into contiguouscontact with the stripping face of said second layer, placing the firstand second layers in a vulcanizing press and vulcanizing the two layerstogether, cutting through the printing face of said first layer down tosaid stripping faces in a given pattern and stripping the pattern ofsaid first layer from said second layer to leave indicia for printing atsaid printing face of said first layer.
 2. The method as claimed inclaim 1, wherein said rubber composition of said engraveable layer is avulcanizable natural rubber or a vulcanizable polyblend of polyvinylchloride and a nitrile rubber and said rubber composition of said baselayer is a vulcanizable nitrile rubber.
 3. The method as claimed inclaim 2, wherein the Shore Durometer (Shore A) Hardness of theengraveable layer and the base layer are on the order of 50 - 55.